A method and apparatus for automated tissue assay is disclosed in U.S. Pat. No. 5,355,439. The apparatus operates by determining particular tests to be applied to a plurality of samples. Each test comprises a number of distinct steps, with respective starting times and completion times. The apparatus schedules the steps of multiple tests into a single time sequence by interleaving the steps of different tests. Time conflicts that result from interleaving the various starting and completion times are resolved by adjusting the duration of one or more of the steps.